Glaucoma is a group of eye conditions resulting in damage to the optic nerve. The World Health Organization has identified glaucoma as the second leading cause of blindness in the world. It is estimated that glaucoma was the cause of blindness in 8.4 million people globally in 2010, rising to 11.2 million by 2020. Increase in intraocular pressure (“IOP”), or fluid pressure within the eye, is considered to be one of the factors that cause glaucoma. IOP levels normally range from 10 mmHg to 21 mmHg, but can be up to 50 mmHg in a diseased eye. Early diagnosis and treatment of abnormally high IOP can minimize or prevent optic nerve damage and limit glaucoma-related vision loss. Conventionally, IOP is measured by tonometry, which requires an ophthalmologist visit. As a result, several months may pass between IOP measurements, which is far less frequent than known circadian fluctuations of IOP. Moreover, glaucoma can be a painless disease that progresses gradually over a long time period, typically rendering it unnoticeable until a loss of vision or irreversible nerve damage occurs. Early diagnosis and treatment can minimize or prevent such a result.
Conventional devices directed towards continuous IOP monitoring suffer from several drawbacks. For example, many conventional devices require surgery (e.g., implanting the IOP sensing device in the anterior chamber of the eye, embedding the IOP sensing device in an implantable prosthetic lens, etc.). On the other hand, many non-invasive conventional devices measure pressure indirectly and thus are inherently inaccurate. For example, one such conventional device includes an IOP sensing device embedded within a contact lens. Pressure is measured indirectly by corneal curvature as measured by a strain gauge. The accuracy of the IOP measurements, however, are affected as a result of variation of the cornea thickness and diameter.